A single screening test for Chlamydia trachomatis failed to reduce the risk of pelvic inflammatory disease through one year, researchers reported.

Action Points

Explain to interested patients that this study did not support the use of a single, annual screening test for chlamydial infection to reduce the risk of pelvic inflammatory disease in young women.

A single screening test for Chlamydia trachomatis failed to reduce the risk of pelvic inflammatory disease through one year, researchers reported.

Pelvic inflammatory disease developed in 1.3% of women who were immediately screened and treated and 1.9% of those who did not have their baseline samples tested for one year (RR 0.65, 95% CI 0.34 to 1.22), Pippa Oakeshott, MD, of St. George's, University of London, and colleagues reported online in BMJ.

There was a nonsignificant trend toward a lower risk of pelvic inflammatory disease with screening among women who were positive for chlamydial infection at baseline (1.6% versus 9.5%; RR 0.17, 95% CI 0.03 to 1.01, P=0.07).

"Although some evidence shows that screening reduced rates of pelvic inflammatory disease, especially in women with chlamydial infection at baseline, the absolute number of cases prevented was small," Oakeshott and her colleagues wrote.

The findings indicate that 147 women would have to be screened for chlamydial infection or 13 with positive results would have to be treated to prevent one case of pelvic inflammatory disease through one year.

"These numbers are greater than previously suggested," the researchers wrote. Thus, previous estimates of the cost-effectiveness of screening might not be accurate.

Nevertheless, Oakeshott said in an interview, "I do think that screening works."

Oakeshott noted that current recommendations call for annual screening of sexually active women under a certain age -- 26 in the U.S. and 25 in the U.K. -- in addition to repeat testing whenever women get a new sexual partner.

Because more than three-quarters (79%) of the cases of pelvic inflammatory disease in the trial developed in women who tested negative for chlamydial infection at baseline, it is likely that many of the infections occurred during follow-up, Oakeshott said.

For that reason, she said, efforts should be made to emphasize the guidance that women get repeat testing each time they have a new sexual partner.

Although screening programs have been implemented in the U.S. and the U.K., good evidence of the effectiveness of such programs is lacking, according to Oakeshott and her colleagues. The only two previous trials of screening programs conducted in the U.S. and Denmark identified about a 50% reduced risk of pelvic inflammatory disease, but they have been criticized for methodological flaws.

To further explore the issue, the researchers conducted a randomized controlled trial, called the POPI (Prevention of Pelvic Infection) trial.

The swabs were either screened immediately (1,254 women) or stored for one year and then analyzed (1,265 women).

All of the participants were advised to get checked independently if they thought they were at risk for chlamydial infection.

The baseline prevalence of chlamydial infection was 5.4% among the screened women and 5.9% in the controls (based on testing of the swabs one year later).

Through follow-up, slightly more women in the screened group reported symptoms (34% versus 31.3%) -- including pelvic pain, dyspareunia, bleeding between menstrual periods, abnormal vaginal discharge -- but a similar number of women in each group reported having at least two sexual partners and using condoms.

About one-fifth (22%) of the women in the trial received independent testing for chlamydia during follow-up, which might have reduced the effect of screening, according to the researchers.

In an accompanying editorial, Jessica Sheringham, MA, MSc, of University College London, said "it is disappointing but not surprising that this study could not provide a clear answer as to whether screening is effective in reducing the incidence of pelvic inflammatory disease."

Nevertheless, the findings provide important insights, she said.

The justification for investing resources in screening for chlamydial infection has been based primarily on the assumption that it would prevent pelvic inflammatory disease, thought to be prevalent enough to cause a public health problem.

The findings of the current study, however, suggest that the incidence of pelvic inflammatory disease might be lower than expected and that Chlamydia might not be responsible for most of the cases, Sheringham said.

Oakeshott and her colleagues acknowledged that the trial was underpowered, the findings might have limited generalizability to other populations, some of the women's medical records were incomplete, and the diagnosis of pelvic inflammatory disease lacks sensitivity and specificity.

The study was supported by the Bupa Foundation. TMA sample collecting kits were provided by Gen-Probe.

The study authors reported no conflicts of interest.

Sheringham reported no financial conflicts of interest. One of the co-authors of the POPI trial is a member of her PhD supervisory panel. Sheringham's research involves evaluating the delivery of the national chlamydia screening program.

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